This incident is very clear cut, and don´t need a lot of clarification nor justification. The Brits is an arse, and he behave like a moron in Thailand. it very simple today, to understand that other people do not want cigarette smoke in their eyes or breath in. it´s normal and respectful behavior to walk aside for the need to smoke. You should especially not smoke where there is a sign that tell you to not do, as well as respect when someone point that fact out to you.
That´s the only thing that need to be said. The Brit is 100% wrong, and the Thais did nothing wrong at all. Doesn´t matter how the law is and what is forbidden or permitted. It´s all about understanding, respect and common sense. He just better stay home, as he lacks all of them.